**3.3.4 Effect of bauxite and wet strength agent on dry tensile strength**

Fig.3-6 showed the effect of bauxite and wet strength agent on dry tensile strength when other factors held at 0 level. When bauxite was near 0 level, the dry tensile strength increased with the increase of wet strength agent, when bauxite was higher than the zero level, with the wet strength agent increased, the dry tensile strength first increased and then

Fig.3-4 showed the effect of grammage and rosin on dry tensile strength when other factors were held at 0 level. Dry tensile strength significantly increased with the increase of grammage; when grammage was small, dry tensile strength slowly decreased with the amount of rosin increases, this was because bonding effect of the additive rosin to fibre became larger, when the grammage was large, dry tensile strength slowly increased with the amount of rosin increase, the maximum occurred when rosin was held at 1.2%, and grammage was held at 110 g/m2. With the grammage increased, the number of fibre in per area increased, bonding between the fibres enhanced, the strength increased, at this moment, the positive effect of grammage on strength was much greater than the negative

Fig. 3-4. Response surface and contour plots for the effects of grammage and rosin on dry tensile strength: beating degree was held at 40SR°, bauxite was held at 4%, wet strength

Fig.3-5 showed the effect of grammage and rosin on dry tensile strength when other factors were held at 0 level. Adding the amount of bauxite at a low level, the dry tensile strength decreased with the increase of added rosin amount; adding the amount of bauxite at a high level, the added rosin amount almost had no effect on the dry tensile strength, maximum of the dry tensile strength occurred when bauxite was held at 4%, and rosin was held at 0.4%,

Fig.3-6 showed the effect of bauxite and wet strength agent on dry tensile strength when other factors held at 0 level. When bauxite was near 0 level, the dry tensile strength increased with the increase of wet strength agent, when bauxite was higher than the zero level, with the wet strength agent increased, the dry tensile strength first increased and then

because rosin adsorption has been saturated, there was no effect on the strength.

**3.3.4 Effect of bauxite and wet strength agent on dry tensile strength** 

**3.3.3 Effect of rosin and bauxite on dry tensile strength** 

**3.3.2 Effect of grammage and rosin on dry tensile strength** 

impact of rosin.

agent was held at 1.8%

decreased, the maximum occurred when wet strength agent was held at 2%, and bauxite was held at 3.5%. This is because with the adding of the wet strength agent, the adsorption of the fibre system to wet strength agent had already been saturated, and it no longer played a role in increasing strength, anionic trash in absorption system impacted the combination between the fibre, leading to strength decreased.

Fig. 3-5. Response surface and contour plots for the effects of rosin and bauxite on dry tensile strength: beating degree was held at 40SR°, grammage was held at 80 g/m2, wet strength agent was held at 1.8%

Fig. 3-6. Response surface and contour plots for the effects of bauxite and wet strength agent on dry tensile strength: beating degree was held at 40SR°, grammage was held at 80 g/m2, rosin was held at 0.8%
